Showing papers by "Abdul Hai Alami published in 2017"

One-step synthesis and deposition of few-layer graphene via facile, dry ball-free milling

Abstract: Graphene is a 2-D carbon material showing considerable prominence in a wide range of optoelectronics, energy storage, thermal and mechanical applications. However, due to its unique features which are typically associated with difficulty in handling (ultra-thin thickness and hydrophobic surface, to name a few), synthesis and subsequent deposition processes are thus critical to the material properties of the prepared graphene films. While existing synthesis approaches such as chemical vapor deposition and epitaxial growth can grow graphene with high degree of order, the costly high temperature and/or high vacuum process prohibit the widespread usage, and the subsequent graphene transfer from the growth substrates for deposition proves to be challenging. Herein, a low-cost one-step synthesis and deposition approach for preparing few-layer graphene (FLG) on flexible copper substrates based on dry ball-free milling of graphite powder is proposed. Different from previous reports, copper substrates are inserted into the milling crucible, thus accomplishing simultaneous synthesis and deposition of FLG and eliminating further deposition step. Furthermore, while all previously reported high energy milling processes involve using balls of various sizes, we adopt a ball-free milling process relying only on centrifugal forces, which significantly reduces the surface damage of the deposition substrates. Sample characterization indicates that the process yields FLG deposited uniformly across all tested specimens. Consequently, this work takes graphene synthesis and deposition a step closer to full automation with simple and low-cost process.

Experiments on polymer welding via concentrated solar energy

Abstract: This work presents the experimental assessment of a facile and effective method for polymer welding. The setup includes a 20-cm-diameter clear crystal sphere that concentrates solar energy onto an infinitesimally small point (0.8 mm). The motion of this focal point performs the welding operation, which is controlled with good precision by a computer-numerical control (CNC) machine that lays the path and executes it. An x-y-z platform follows the desired programmed trajectory to weld the workpiece that consists of two thin sheets of polymers, one transparent and the other opaque to be joined by transmission welding. The welding process is investigated at different speeds to determine the optimum traverse rate and focal point energy density combination for a strong weld with minimal thermal damage to the substrates. The samples are studied under the microscope, and the welding strength is determined by tensile test to establish the feasibility of the process.